The Gresley Manuscript was discovered in 1984. It is held at the Derbyshire Record Office. It contains very early descriptions of music and dance in England, and was made sometime between 1480 and 1520. Some links for the Gresley MS. Images of the original MS are copyright and will not be available any time soon.
Treasure 10: the Gresley Dance Manuscript Derbyshire Records Office. 
Norman Gray's Notes on the Gresley Dance Collection 
The Gresley Dance Collection. This article appeared in volume 5 of the Letter of Dance. 
The Gresley Dance Collection, c.1500 David Fallows, RMA research chronicle xxix (1996) pp.1-20.
Dances from the Gresley Manuscript - Circa 1500 Robert Huggat, 2002 
Dance Steps and Music in the Gresley Manuscript; with music notation; Jennifer Nevile, Historical Dance Volume 3, Number 6, 1999 
Dance in early Tudor England: an Italian connection? Jennifer Nevile, Early Music, May 1998
Court Revels, 1485-1559 W.R. Streitberger,
Book and CD of the dances and tunes available from the Historical Dance Society
Cherwell Thy Wyne, The York Waits; Dances of fifteenth-century England from the Gresley manuscript. Free pdf files of the arrangements from the CD.